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Cassiniís orbit tightens even further as the spacecraft begins its 71st orbit around the Ringed Rlanet, the 7.1-day-long Rev70. The shorter orbit lends itself to a more dedicated set of observations, including imaging of Saturnís atmosphere, rings, and several of its moons, including Enceladus. Cassini begins Rev70 on May 29 at its farthest distance from Saturn, called apoapsis. At this point, Cassini is 1.27 million km (786,000 mi) from Saturn. The high inclination of this orbit allows for detailed study of Saturnís ring system and northern hemisphere from high above the ring plane. On May 30, Cassini ISS will acquire a medium-resolution azimuthal scan of the F ring, outer A ring, and Cassini Division. Cassini will perform a similar scan on May 31 on the left and right ansae of the outer A ring (including the Keeler and Encke Gaps). On May 30, Cassini performs several observations of Saturnís small, inner satellites. The observations are designed to study the orbits of these objects and how they might evolve over short periods due to perturbations from the other satellites in the system. On June 1, Cassini reaches periapse, its closest point to Saturn on Rev70. At that point, Cassini will be 163,000 km (101,000 mi) from Saturnís cloud tops. Near periapse, Cassini will quickly pass high over the north polar region of Saturn before descending below the ring plane 15 minutes before periapse. Prior to periapse, Cassini will observe Saturnís north polar region with ISS and the Ultraviolet Imaging Spectrometer (UVIS), in a search for auroral activity. An hour after closest approach, Cassini ISS and the Composite Infrared Mapping Spectrometer (CIRS) will observe Enceladus from a distance of 284,000 km (176,500 mi). This sequence will provide an opportunity to image Enceladusí sub-Saturn hemisphere at 1.7 km (1.1 mi) per pixel. On June 2, Cassini ISS will perform two rings observations. The first is a high-resolution observation of the inner Cassini Division, including the Huygens Ringlet. The second is a partial azimuthal scan covering the outer A ring, and particularly the Keeler Gap, a narrow clearing created by the presence of the small moon Daphnis. On June 4, Cassini ISS will perform several dark current calibration sequences. These calibration images are needed to characterize possible changes in the properties of the wide-angle cameraís CCD detector. Also on June 4, Cassini ISS will acquire a three-frame mosaic of Saturnís atmosphere shortly after Cassini passes above the ring plane. The equatorial viewpoint allows Cassini to view cloud features in both northern and southern hemispheres.
Cassini begins the following orbit, Rev71, on June 5. Rev71 includes distant observations of Enceladus, Mimas, Titan, and Saturnís atmosphere and rings.
Image products created in Celestia. Enceladus basemap by Steve Albers.